EPA takes initial step in regulating aircraft engine GHGs

On July 25, the U.S. EPA finalized a determination under the Clean Air Act that greenhouse gas (GHG) emissions from certain types of aircraft engines contribute to the pollution that causes climate change and endangers American’s health and the environment. According to the EPA, the findings are for carbon dioxide, methane, nitrous oxide, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). The finding is primarily aimed at engines used on large commercial jets. It does not apply to small piston-engine planes, the type often used for recreational purposes, or to military aircraft.

“Addressing pollution from aircraft is an important element of U.S. efforts to address climate change. Aircraft are the third largest contributor to GHG emissions in the U.S. transportation sector, and these emissions are expected to increase in the future,” said Janet McCabe, EPA’s acting assistant administrator for air and radiation. “EPA has already set effective GHG standards for cars and trucks and any future aircraft engine standards will also provide important climate and public health benefits.”

The action taken by the EPA on July 25 doesn’t set emissions standards for aircraft engines. Rather, the endangerment finding is an initial step the EPA must take prior to adopting GHG engine standards. According to the EPA, the International Civil Aviation Organization is expected to formally adopt its environmental committee’s February 2016 agreement on international aircraft CO 2 standards in March 2017. The agency also indicated it expects to move forward on standards that would be at least as stringent as those standards.

In a statement, the EPA said U.S. aircraft emit roughly 12 percent of GHG emissions from the U.S. transport sector and 29 percent of GHG emissions from all aircraft globally. Overall, aircraft emit 3 percent of total U.S. GHG emissions and 0.5 percent of total global GHG emissions. A similar endangerment finding was released by the EPA in 2009 regarding GHG emissions from new cars and light trucks.

The EPA first proposed to find GHG emissions from certain classes of engines used in aircraft contribute to climate change and the endangerment of public health in mid-2015. A comment period on the proposal closed last year.

Within the final rule, the EPA responded to comments regarding the impact of biofuels on aircraft emissions. According to the EPA, at least one commenter expressed concern about the EPA’s proposed endangerment finding because it does not differentiate between carbon dioxide emissions that result from the combustion of fossil fuels and those that result from biomass or biofuels. The EPA said the commenter argued that such crop-related biogenic emissions should be excluded from the endangerment finding because the carbon dioxide released back to the atmosphere when emitted from crop-derived biogenic sources contains the same carbon that was previously removed or sequestered from carbon dioxide in the atmosphere. As such, that carbon dioxide doesn’t contribute to elevated atmospheric concentrations of GHGs.

The agency did not amend its rulemaking based on the comments on biogenic emissions. In its response, the EPA said “all CO2 emissions, regardless of source, influence radiative forcing equally once it reaches the atmosphere and therefore there is no distinction between biogenic and non-biogenic CO2 regarding the CO2 and the other well-mixed GHGs within the definition of air pollution that is reasonably anticipated to endanger public health and welfare.” The EPA further explains that the fact that carbon dioxide emission originate from carbon-based fuels crated through different processes is not relevant to defining the air pollution that is reasonably anticipated to endanger public health and welfare.

A full copy of the final rule for the endangerment finding can be downloaded from the EPA’s website.